It is possible to play mp3pro with MB, although it's a bit tricky.
In WA it is necessary to check the option "Enable (use mp3pro decoder for all .mp3 files)" in order to activate the plugin.

I don't remember well, but there was some problem with normal mp3 files, either with playback quality or with plugin tag editor, I might be wrong,though.
Anyway, this trick does not work in MB, which always plays the files with mp3 extension (including mp3pro files) with default bass library.
So, one can use a bit "modified" version of the plugin which recognize a different extension than mp3, say mpp, mp1, mpa, even mp3pro

This trick I've used in WA and it works here in MB as well.
I've experimented a bit with different extensions for mp3pro files (using respective plugin) and found the following pros and cons:
*.mpp - it can be played, however
- the original tags (ID3v1/2) are not recognized
- technical details of the file are not recognized (bitrate, frequency, duration) are not recognized
+ new tags can be added to the file, they are appended at the end of file as APE tags
- this extension is used for old musepack files, so maybe this is the reason for the flaws above, just the bass plugin things that this is a mpc/mpp file
*.mpa - it's playable,
+ the technical details are obtained, except the sampling frequency, which is displayed as twice lower, i.e. 22 kHz
- the original tags (ID3v1/2) are not recognized
- new tags cannot be added to the file, they are stored in MB library instead
- this extension is used by mpeg1 audio files (I think), but I doubt that somebody has such files in his library
*.mp3pro - the same as *.mpa, except that the extensin is "unique"
*.mp1 - maybe the best solution so far
+ technical details are recognized, just the sampling rate is wrong (22 kHz)
+ the original tags (ID3v1/2) are recognized
+ new tags can be added to the file as to a normal mp3 file
- the extension is not "free", but again, I doubt that somebody has mp1 audio files
I've put a zip file with these modified plugins
here , try and choose the best way for you.
Ah, something more, this workaround will work with stored files only, not with streams (obviously), which have mp3 extension.
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